Hi Bill,

The Steam Era Freight Cars website is your friend.  See the files for different 'species' of steel boxcars created by Ed Hawkins, Ted Culotta and others, specifically the files for 10' Postwar Boxcars for these GN cars.

I believe the Intermountain kit represents GN 10900-11874 and 18000-19499, all build at St. Cloud Shops in 1948-49.  Handbrakes were Ajax or Universal, running boards were Morton, Apex or Gypsum, depending on the car series (there were about 7 series), and I think the running boards were painted Mineral Red and the trucks and underframe were black when new.  The doors also varied by series.  There are lots of online photo sources: Fallen Flags and Google images are just two.  Using Google images will get you to other sites.

Todd Sullivan.